Ascites tumor cells seem to place great demand upon fatty acids as a source of metabolic energy. Spector and Steinberg observed that 70% of the cellular oxygen uptake of Ehrlick tumor cells was attributed to the oxidation of fatty acids. Spector and Steinberg and more recently our group demonstrated that ascites tumor cells possess pronounced lipolytic activities. However, beyond recognition that ascites tumor cells do conduct lipolysis there is little additional information available on this potentially important metabolic activity of tumor cells. Preliminary studies in our laboratory indicate that Walker 256 ascites tumor cells possess at least two distinct lipolytic activities with clearly different pH and temperature sensitivities; one with a pH optimum of between 4.6 and 4.8 and sensitive to cold and another with a pH optimum of about 7.4 to 8.2 and heat sensitive. Acid lipases have only recently been recognized in normal animal cells and appear to represent lysosomal enzymes. The broad objectives of the proposed study are to describe in detail the lipolytic activities of this cancer cell, to investigate the mechanisms regulating these lipolytic activities, and to compare this information to that available for lipolysis in normal cells. Specifically, studies will be conducted, using Walker 256 tumor cells in ascites form, of the subcellular distribution of lipase enzymes, substrate specificity of these enzymes, and of the ability of known stimulators and inhibitors of lipolysis to influence these activities. Further studies will involve measurements of tumor cell lipoprotein lipase activity since we have observed that ascites fluid contains appreciable lipoprotein-triglyceride and this conceivably could serve as substrate for the tumor cells. In summary, little information is available on the lipolytic activities of cancer cells. Obtaining additional information would seem important since the discovery of chemotherapeutically exploitable differences between normal and cancerous cells is based upon understanding and contrasting the metabolism of such cells whenever possible.